Rule: Use SS304 / CF8 for general water and mild process. Use SS316 / CF8M when chlorides, many chemical services, or marine-adjacent duty require molybdenum. Upgrade further to duplex when PREN still falls short — see duplex vs SS316.
SS304 vs SS316 Valves
ASTM A351 CF8 (304) vs CF8M (316) — the most common stainless upgrade decision on ball, gate, globe, butterfly and check RFQs.
| Factor | SS304 / CF8 | SS316 / CF8M |
|---|---|---|
| Molybdenum | None (typical) | ~2–3% Mo — better pitting resistance |
| Chlorides | Limited | Better — still not seawater duplex/NAB |
| Relative cost | Lower | Higher |
| Typical RFQ use | Water, air, mild chemicals, PN16 utility | Chemical, pharma, chloride process, Class 150–800 |
Manufacturer pages: SS304 ball · SS316 ball · SS304 gate · SS316 gate · SS304 PN16 ball RFQ · SS316 Class 150 ball RFQ · SS304 PN16 butterfly RFQ.
FAQ
Is CF8 the same as SS304?
CF8 is the cast equivalent of wrought AISI 304. CF8M is the cast equivalent of AISI 316.
When must I use SS316 instead of SS304?
When chlorides, many acids, or marine-adjacent service require molybdenum for pitting resistance.
Is SS316 always worth the cost?
No. Non-chloride utility water and mild service usually allow CF8 / SS304.